How to Change Default Application to Open File Type?

Ive got these Divx files that I want to open by default with yxflash, but whenever I click em, android pops just the movies and Act1 players, never the yxflash. Is there a way to force it to show it as an option and make it default?

No, because the .avi files arent set to any default application, but upon click I get only 2 choices, Movies and Act 1, and I dont want to chose any of those. yxflash isnt showing as an option, so I was wondering if there was a workaround or any other way to set them to open with yxflash by default